GENETIC AND MOLECULAR STUDIES FOR CHARACTERS RELATED TO COTTON LEAF WORM RESISTANCE IN SOYBEAN

Abstract

A three year–field experiment was carried out in Giza Agric. Exp. & Res. St., A.R.C., Giza Governorate, Egypt, during 2008, 2009 and 2010 seasons. Five soybean genotypes (four resistant and one susceptible) and their hybrids were evaluated for the resistance of cotton leaf worm (Spodopetra littoralis). Under field conditions, soybean plants were not subjected to chemical control to determine percentage of rating levels of leaflets area consumed by leaf feeding larvae of cotton leaf worm. This percentage also was determined under laboratory conditions. The results indicated that soybean genotypes; Giza 111, Giza 22, L 158, L127, hybrid 4, hybrid 5, hybrid 7 and hybrid 10 were resistant for cotton leaf worm, whereas, the susceptible parent Dr–101, hybrids 1 and 6 showed the reverse trend. This study confirmed the relationship between pubescence density and feeding preference by cotton leaf worm for leaflets of soybean genotypes. High concentrations of Jasmonic acid in leaflets of the resistant soybean genotypes reflected positively on the yield. SDS-protein PAGE exhibited bands 13 and 14 with MW of 55 and 40 KDa, respectively, as markers for the resistant parents and hybrids. The ISSRs analysis was performed using 15 primers with soybean genotypes, yielded 135 and 91 total number of amplified and polymorphic fragments, respectively. Five markers were detected using four primers for cotton leaf worm resistance. The present study focused on the characterization of genetic diversity among the tested soybean genotypes using SDS-protein and ISSRs-DNA markers to determine their resistance and/or susceptibility to cotton leaf worm.

Key words: Soybean, genotypes, Cotton leaf worm, Pubescence density, Jasmonic acid, ISSRs.